ES2925576T3 - Acylphosphine oxide initiators - Google Patents

Abstract

An acylphosphine oxide initiator in which the acyl group is selected from the group consisting of a benzoyl group substituted by a urea group or an oxalylamide group; a 2,6-dimethylbenzoyl group substituted at the 3-position by a urea group or an oxalylamide group; a 2,6-dimethoxybenzoyl group substituted at the 3-position by a urea group or an oxalylamide group; a 2,4,6-trimethylbenzoyl group substituted at the 3-position by a urea group or an oxalylamide group; and a 2,4,6-trimethoxybenzoyl group substituted at the 3-position by a urea group or an oxalylamide group. (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Acylphosphine oxide initiators

field of invention

The present invention relates to specific acylphosphine oxide initiators and their use in UV curable compositions, especially UV curable inkjet inks.

Background of the invention

Inkjet is changing the way designers approach interior decoration and fashion. Rotogravure, screen printing and flexography are gradually being replaced by industrial inkjet printing systems, as these allow short runs and low-cost manufacturing of personalized products. UV curable inkjet is especially preferred as a technology since it is capable of reliably providing high image quality on non-absorbent substrates.

However, a disadvantage of jetting UV curable inks is that odor control measures need to be taken to deal with residual monomers after UV curing in a printed article for interior decoration. While the photoinitiators themselves are rarely volatile, several of their degradation products are volatile enough to generate odors and potential toxicological hazards. In interior decoration it is especially important to limit these volatiles to minimize bad odor and toxicological risks.

Acylphosphine oxide type photoinitiators are a particularly important class of photoinitiators, especially for LED curable compositions, which are becoming more and more important in radiation curing technology. However, acylphosphine oxide type photoinitiators have a tendency to form volatile aldehydes, such as mesitaldehyde, upon cleavage and hydrogen transfer.

Functionalization of acylphosphine oxide on the mesitaldehyde fragment is the most obvious approach to avoid mesitaldehyde formation. Various approaches have been disclosed in the patent literature.

WO 2014/051026 (FUJIFILM) and WO 2014/129213 (FUJIFILM) disclose a bromination strategy to functionalize benzylic positions in acylphosphine oxide-type photoinitiators, followed by subsequent derivatization of intermediate bromides to prepare photoinitiators of oligomeric or polymerizable acylphosphine oxide. The benzylic bromination of acylphosphine oxide, which has multiple benzylic positions, is a statistical process, which carries the risk of formation of a mixture of unbrominated and multibrominated mesitaldehyde groups, which still results in the appearance of volatile degradation products. formed from the mixture of functionalized photoinitiators.

Synthesis of isocyanate-functional acylphosphine oxide photoinitiators are disclosed in JP 2014196425 (FUJIFILM) and WO 2014/129213 (FUJIFILM). Isocyanate-functional acylphosphine oxide photoinitiators are further converted to carbamate-functional photoinitiators. However, there is often a reluctance to use carbamates due to their potential toxicity. Chronic encephalopathy is known to result from prolonged exposure to small doses of carbamates.

The use of chloromethylated acylphosphine oxide photoinitiators has been disclosed in WO 2013/091521 (SHENZHEN UV CHEMTECH). The chloromethylated acylphosphine oxide photoinitiators are further converted to the final photoinitiators. Chloromethylation reactions often produce bis(chloromethyl) ether, which is highly carcinogenic, as a byproduct.

Polymerizable bisacylphosphine oxide photoinitiators for use in photopolymerizable dental materials have been disclosed in US 2007027229 (IVOCLAR VIVADENT) and JP 2012062280 (KURARAY MEDICAL). Although advantageous for dental applications, the poor solubility of bisacylphosphine oxide photoinitiators makes it difficult for the formulator to use them in inkjet inks.

Furthermore, it is known that the carbon-phosphorus bond in acylphosphine oxides is easily broken by nucleophilic compounds such as water and alcohol. Thus, the photoinitiator is gradually degraded, leading to a loss of activity of the initiators. However, unreacted acylphosphine oxide in a printed interior décor item can release volatile aldehydes, such as mesitaldehyde, when cleaned with a cleaning fluid, which typically contains water or alcohol.

There is still a need for efficient and stable acylphosphine oxide photoinitiators that smell shortly after curing of UV curable inkjet inks used for interior decoration applications.

Summary of the invention

In order to overcome the problems described above, preferred embodiments of the present invention have been made using specific acylphosphine oxide photoinitiators as defined in claim 1.

Functionalized acylphosphine oxide photoinitiators with highly dipolar self-complementary functional groups on mesitaldehyde, selected from the group consisting of a urea group and an oxalylamide group, were found to be particularly effective in reducing the odor of a UV-curable composition. cured. The figure below illustrates how volatile compounds are believed to interact to result in malodour reduction.

oxalylamide urea

hydrogen bond formation and hydrogen and dipole double dipole bond formation

An object of the present invention is to provide a new class of functionalized acylphosphine oxide photoinitiators.

Another object of the present invention is to provide a UV radiation curable composition comprising at least one acylphosphine oxide photoinitiator according to the present invention.

Another object of the present invention is to provide a UV curable inkjet ink comprising at least one acylphosphine oxide photoinitiator according to the present invention.

These and other objects will become apparent from the following detailed description.

Description of achievements

Definitions

The term "multifunctional acylphosphine oxide" means that the acylphosphine oxide initiator includes more than one phosphine oxide group.

The term "alkyl" refers to all possible variants of each number of carbon atoms in the alkyl group, i.e., methyl and ethyl, three carbon atoms: n-propyl and isopropyl, four carbon atoms: n-butyl , isobutyl and tert.-butyl, with five carbon atoms: n-pentyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl and 2-methylbutyl, etc.

The term "substituted", in eg a substituted alkyl group, means that the alkyl group may be substituted by other atoms than those usually present in such a group, ie carbon and hydrogen. For example, a substituted alkyl group can include a halogen atom or a thiol group. An unsubstituted alkyl group contains only carbon atoms and hydrogen atoms.

Unless otherwise specified, a substituted alkyl group, a substituted alkenyl group, a substituted alkynyl group, a substituted aralkyl group, a substituted alkaryl group, a substituted aryl group and a substituted heteroaryl group are preferably substituted by one or more selected substituents. from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert.-butyl, ester, amide, ether, thioether, ketone, aldehyde, sulfoxide, sulfone, sulfonate ester, sulfonamide, -Cl, -Br, -I, -OH, -SH, -CN and -NO2.

Unless otherwise specified, a substituted or unsubstituted alkyl group is preferably a C1 to C6 alkyl group.

Unless otherwise specified, a substituted or unsubstituted alkenyl group is preferably a C2 to C6 alkenyl group.

Unless otherwise specified, a substituted or unsubstituted alkynyl group is preferably a C2 to C6 alkynyl group.

Unless otherwise specified, a substituted or unsubstituted aralkyl group is preferably a phenyl or naphthyl group including one, two or more C1 to C6 alkyl groups.

Unless otherwise specified, a substituted or unsubstituted alkaryl group is preferably a C7 to C25 alkyl group including a phenyl or naphthyl group.

A cyclic group comprises at least one cyclic (ring) structure and can be a monocyclic or polycyclic group, ie one or more rings are fused.

A heterocyclic group is a cyclic group that comprises atoms of at least two different elements as members of its ring(s). The counterparts of heterocyclic groups are monocyclic groups whose ring structures are composed solely of carbon. Unless otherwise specified, a substituted or unsubstituted heterocyclic group is preferably a pentagonal or hexagonal ring substituted by one, two, three or four heteroatoms which are preferably selected from oxygen atoms, nitrogen atoms, sulfur atoms, selenium or combinations thereof.

An alicyclic group is a non-aromatic homocyclic group whose ring atoms are composed of carbon.

The term "heteroaryl group" refers to a monocyclic or polycyclic ring comprising carbon atoms and one or more heteroatoms in the cyclic structure, preferably 1 to 4 heteroatoms, which are independently selected from nitrogen atoms, oxygen atoms, selenium and sulfur atoms. Preferred examples of heteroaryl groups include, without limitation, pyridinyl, pyridazinyl, pyrimidyl, pyrazyl, triazinyl, pyrrolyl, pyrazolyl, imidazolyl, (1,2,3,)- and (1,2,4)-triazolyl, pyrazinyl , pyrimidinyl, tetrazolyl, furyl, thienyl, isoxazolyl, thiazolyl, isoxazolyl, and oxazolyl. A heteroaryl group may be substituted or unsubstituted by one, two or more suitable substituents. Preferably, a heteroaryl group is a monocyclic ring, the ring comprising 1 to 5 carbon atoms and 1 to 4 heteroatoms. More preferably, a substituted or unsubstituted heteroaryl group is preferably a five or six membered ring substituted with one, two or three oxygen atoms, nitrogen atoms, sulfur atoms, selenium atoms, or combinations thereof.

Unless otherwise specified, an unsubstituted aryl group is preferably a phenyl or naphthyl group.

Unless otherwise specified, an acyl group is preferably a -C(=O)-R group in which R is selected from the group consisting of a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkaryl group and substituted or unsubstituted aralkyl group.

Acylphosphine oxide initiators

In a preferred embodiment of the invention, the photoinitiator is an acylphosphine oxide initiator in which the acyl group is selected from the group consisting of a benzoyl group substituted by a urea group or an oxalylamide group, a 2,6-dimethylbenzoyl group substituted in the 3-position by a urea group or an oxalylamide group, a 2,6-dimethoxybenzoyl group substituted in the 3-position by a urea group or an oxalylamide group, a 2,4,6-trimethylbenzoyl group substituted in the 3-position by a urea group or an oxalylamide group and a 2,4,6-trimethoxybenzoyl group substituted at the 3-position by a urea group or an oxalylamide group, with the proviso that the acylphosphine oxide initiator does not contain any thiol group if the acyl group includes a group urea.

In a particularly preferred embodiment, the acylphosphine oxide initiator is represented by Formula (I):

Formula (I),

in which R1 represents a group according to Formula (II):

Formula (II),

in which

* represents the point of attachment to the phosphine oxide group in Formula I),

R2 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or OR8, R3 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or a group represented by Formula (II),

R4, R5 and R6 independently represent a hydrogen, methyl or methoxy atom,

R7 and R8 independently represent a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted aralkyl group , a substituted or unsubstituted alkaryl group, a substituted or unsubstituted heteroaryl group, a group comprising (meth)acrylate or a group comprising (meth)acrylamide, and

n represents the integer 0 or 1.

In another particularly preferred embodiment, the acylphosphine oxide initiator is represented by Formula (III):

Fórmula (III),

Formula (III),

in which

R2 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or OR8, R3 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or a group represented by Formula (II),

Fórmula (II),

Formula (II),

* represents the point of attachment to the phosphine oxide group in Formula (I),

R4, R5 and R6 independently represent a hydrogen, methyl or methoxy atom,

R7 and R8 independently represent a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted aralkyl group , a substituted or unsubstituted alkaryl group, a substituted or unsubstituted heteroaryl group, a group comprising (meth)acrylate or a group comprising (meth)acrylamide,

L represents a divalent linking group containing 2 to 50 carbon atoms, and

n represents the integer 0 or 1.

In the acylphosphine oxide initiator according to Formula (I) and Formula (III), the substituents R4, R5 and R6 preferably represent methyl. This improves the stability of the acylphosphine oxide initiator, since the introduction of a methyl group in the ortho position protects the carbonyl group from nucleophilic attack.

In the acylphosphine oxide initiator according to Formula (I) and Formula (III), the substituent R2 is preferably a phenyl group for reasons of stability.

In the acylphosphine oxide initiator according to Formula (III), the linking group L is preferably a substituted or unsubstituted alkylene group or a substituted or unsubstituted alkoxylated group. The linking group L is preferably further substituted by a group selected from the group consisting of a diester, a diamide and a dicarbamate, with a diester and a dicarbamate being particularly preferred. In a particularly preferred embodiment, the linking group L is further substituted by a group selected from the group consisting of:

The acylphosphine oxide initiator according to the present invention is preferably a polymerizable photoinitiator, a polymeric photoinitiator or a multifunctional photoinitiator.

In a more preferred embodiment, the multifunctional photoinitiator according to the present invention is a difunctional initiator, ie a photoinitiator containing two acylphosphine oxide moieties, more preferably two monoacylphosphine oxide moieties in which the acyl groups are bonded to each other. With this last structure, a more effective reduction of the bad smell is achieved by curing by UV radiation.

In another preferred embodiment, the photoinitiator according to the present invention is a polymeric photoinitiator having a molecular weight of at least 1000 Daltons. The weight average molecular weight Mw of the polymeric photoinitiator according to the present invention is preferably less than 10,000 Daltons, more preferably less than 5,000 Daltons, and most preferably less than 3,000 Daltons. When the weight average molecular weight Mw is maintained between these ranges, UV curable inks and compositions can be made in which the polymeric photoinitiator does not cause a substantial increase in viscosity, making them suitable for use in inkjet printing. from ink.

The photoinitiator according to the present invention is preferably functionalized with at least one polymerizable group selected from the group consisting of an acrylate, a methacrylate, an acrylamide and a methacrylamide, with an acrylate being particularly preferred.

In a preferred embodiment, the polymerizable group is included in the R7 substituent of the acylphosphine oxide initiator according to Formula (I) and Formula (III).

In a preferred embodiment, the R7 substituent of the acylphosphine oxide initiator according to Formula (I) and Formula (III) is a group comprising acrylate. The latter makes it possible to reduce the odor even more, since, after curing by UV radiation, the volatile aldehydes are incorporated into the polymeric network.

Synthesis methods for acylphosphine oxides are well known to those skilled in the art of initiator preparation. Typical synthesis methods for the acylphosphine oxide type of photoinitiators are disclosed in WO 2006/056541 (CIBA), WO 2005/014605 (CIBA), DE 10206117 (BASF) and WO 2014/016567 (LAMBSON). Specific methods for the synthesis of acylphosphine oxide initiators of the present invention are disclosed in Examples 1 to 7 below.

Low odor acylphosphine oxide photoinitiators according to the present invention, functionalized with an oxalylamide moiety, are shown in Table 1 below, without being limited thereto.

Table 1

Low odor acylphosphine oxide photoinitiators according to the present invention, functionalized with a urea moiety, are shown in Table 2 below, without being limited thereto.

Table 2

UV curable inks and compositions

A preferred embodiment is a UV radiation curable composition including a polymerizable compound and an acylphosphine oxide initiator according to the invention. The UV curable composition is preferably a UV curable ink, more preferably a UV curable inkjet ink.

A UV curable composition may be colorless and may be used as a primer or varnish. If such a UV curable composition can be applied by jet, it can also be called a colorless inkjet ink. A primer is usually applied to improve the adhesion of a printed image, while a varnish is usually applied to influence gloss or as a protective top coat for a printed image.

The amount of the photoinitiator according to the invention in the UV radiation-curable compositions, inks or inkjet inks is preferably between 1% by weight and 25% by weight, more preferably between 3% by weight and 10% by weight. with respect to the total weight of the composition, ink or inkjet ink curable by UV radiation.

In a more preferred embodiment, the UV curable composition also contains one or more colorants, most preferably color pigments. A plurality of these (jet) inks can also be combined to form a set of (jet) inks to provide multi-color images.

Preferably, the organic color pigment is dispersed in the liquid (jet) ink carrier by means of a polymeric dispersant. The UV curable (jet) ink may contain a dispersion synergist to improve the quality and dispersion stability of the ink. Preferably, at least the magenta ink contains a dispersion synergist. A mixture of dispersion synergists can be used to further improve dispersion stability.

For multi-color image printing, UV-curable (jet) ink is part of a set of UV-curable (jet) inks. A preferred set of UV-curable (jet) inks for printing different colors contains at least one or two, but most preferably at least four UV-curable (jet) inks including a photoinitiator according to the invention. The UV-curable (jet) ink set is preferably a CMYK or CRYK UV-curable (jet) ink set. This set of UV curable (jet) inks can also be expanded with additional inks such as violet, green, red, blue and/or orange ink to further increase the gamut of the image. Also, the range of UV-curable inkjet inks can be expanded by combining full-density and low-density inkjet inks. Combining dark and light inks and/or black and gray inks improves image quality by reducing graininess.

The set of UV-curable (jet) inks may also include a colorless UV-curable (jet) ink, such as a varnish or a primer. A varnish is used to enhance the brightness of printed color images. A primer can be used to improve adhesion on difficult substrates such as glass and polypropylene.

Preferably, the set of UV curable (jet) inks also includes a white UV curable (jet) ink. The white UV-curable (jet) ink preferably contains an inorganic white pigment, such as titanium dioxide, more preferably a rutile pigment, having an average particle size of more than 180 nm.

White inkjet inks are generally used for so-called "surface printing" or "back printing" to form a reflection image on a transparent substrate. In surface printing, a white background is formed on a transparent substrate using a white ink and then a color image is printed on it, where the final image formed from the printed side is then displayed. In so-called back printing, a color image is printed on a transparent substrate using color inks, and then a white ink is applied over the color inks, and the color image is viewed through the transparent substrate. In a preferred embodiment, the UV-curable color inkjet ink is jet-applied over the inkjet ink. white injection at least partially healed. If the white ink is only partially cured, improved wettability of the color inkjet ink on the white ink layer is observed.

In a preferred embodiment, the UV radiation-curable inkjet ink contains an organic color pigment in an amount between 6.0% by weight and 13.0% by weight with respect to the total weight of the UV-curable inkjet ink. UV radiation and has a viscosity of at least 16.0 mPa.s at 450C and at a shear rate of 10 s-1. In a more preferred embodiment, a set of UV-curable inkjet inks is composed of at least three UV-curable inkjet inks containing an organic color pigment in an amount between 6.0% by weight and 13%. .0% by weight with respect to the total weight of the inkjet ink curable by UV radiation and each having a viscosity of at least 16.0 mPa.s at 45°C and at a shear rate of 10 s-1.

The UV curable inkjet ink is preferably a so-called 100% solids UV curable inkjet ink. This means that no solvent is present, ie water or an organic solvent. However, sometimes a small amount of water may be present, generally less than 1% by weight or 2% by weight with respect to the total weight of the inkjet ink. This water has not been added intentionally, but enters the inkjet ink through other components in the form of contamination, such as a hydrophilic monomer.

Preferably, the UV curable inkjet ink does not contain any organic solvent. However, it may sometimes be advantageous to incorporate a small amount of an organic solvent to improve adhesion to the surface of a substrate after UV curing. In this case, the amount of solvent added can be in any range that does not cause problems of resistance to solvent and volatile organic compounds (VOC). The amount of organic solvent in the UV radiation curable inkjet ink is preferably between 0% by weight and 10% by weight, more preferably it does not exceed 5.0% by weight with respect to the total weight of the ink. UV curable inkjet ink.

Alternatively, the UV curable (jet) ink or composition includes a substantial amount of solvent and/or water, eg 20, 30 or more wt% water, and/or one or more organic solvents. Such an inkjet ink is often called a hybrid inkjet ink, since the curing of a printed image involves both drying and curing by UV radiation.

A single polymerizable compound may be used for the polymerizable composition of the UV-curable (jet) ink or composition, but a mixture of different polymerizable compounds is typically used to fine-tune ink properties, such as adhesion to a variety of substrates or flexibility.

In a preferred embodiment of the UV curable (inkjet) ink, the polymerizable compound includes one or more acrylate groups. These polymerizable compounds allow very fast curing in many industrial applications.

In another preferred embodiment of the UV curable (inkjet) ink, the polymerizable compound includes one or more polymerizable groups selected from the group consisting of an acrylamide, a methacrylamide, a vinyl ether group, a vinyl ester group, a allylic ether group, an allylic ester group, a vinyl carbonate group and an alkyne group. These polymerizable compounds are preferred for applications where skin irritation may be a problem.

For interior inkjet decoration, the polymerizable compound preferably includes a multifunctional hybrid monomer containing two or more different polymerizable groups per molecule, such as both an acrylate group and a vinyl ether group. A particularly useful monomer is 2-(2-vinyloxyethoxy)ethyl acrylate (VEEA), but other zwitterionic monomers would also be suitable, such as those described in WO 2010/029017 A (AGFA) and EP 2130817 A (AGFA). . Preferably, the UV curable inkjet inks contain more than 20% by weight and more preferably more than 25% by weight or 30% by weight of one or more hybrid multifunctional monomers with respect to the total weight of polymerizable compounds.

In order to obtain good ejection ability, the viscosity of the UV curable inkjet ink at the ejection temperature is preferably less than 50 mPa-s, more preferably less than 30 mPa-s at a shear rate of 10 s- 1 and at an ejection temperature between 30°C and 70°C.

The UV radiation curable inkjet ink preferably has a surface tension in the range of 20 mN/m to 30 mN/m at 250C, more preferably in the range of about 22 mN/m to about 25 mN/m at 250C. In these ranges a good diffusion of the ink is obtained on a wide range of substrates.

The UV curable (jet) ink may furthermore also contain at least one inhibitor to improve the thermal stability of the ink.

The UV curable (jet) ink may furthermore also contain at least one surfactant in order to obtain good diffusion characteristics on a substrate.

Other photoinitiators and coinitiators

In addition to the acylphosphine oxide photoinitiator of the invention, the UV curable (jet) ink or composition may contain one or more other photoinitiators and/or co-initiators.

The photoinitiators in the UV curable (jet) ink or composition are preferably free radical initiators, more specifically a Norrish type I initiator or a Norrish type II initiator. A free radical photoinitiator is a chemical compound that initiates the polymerization of monomers when exposed to actinic radiation through the formation of a free radical. A Norrish type I initiator is an initiator that cleaves upon excitation producing the initiator moiety immediately. A Norrish type II initiator is a photoinitiator that is activated by actinic radiation and forms free radicals by abstraction of hydrogen from a second compound that becomes the true free radical initiator. This second compound is called a co-initiator or polymerization synergist. Both type I and type II photoinitiators can be used in the present invention alone or in combination. Preferably, the UV curable inkjet ink does not include a cationic photoinitiator.

Preferred free radical photoinitiators for interior decoration applications are selected from the group consisting of polymerizable photoinitiators, polymeric photoinitiators, and polyfunctional photoinitiators. A polyfunctional photoinitiator is a photoinitiator having two or more photoinitiating groups, for example two benzophenone groups and one thioxanthone group. In a more preferred embodiment, said one or more other photoinitiators are one or more polymerizable photoinitiators. Such a photoinitiator results in a lower viscosity than a polymeric photoinitiator, while minimizing health risks in interior decoration applications.

For interior decoration applications, polymerizable photoinitiators can be combined with other types of non-polymeric or non-polymerizable photoinitiators in the inkjet ink at concentration levels such that they do not cause health risks.

In CRIVELLO, JV, et al. , Photoinitiators for Free Radical Cationic & Anionic Photopolymerization, 2nd edition, edited by BRADLEY, G., London, UK: John Wiley and Sons Ltd, 1998. pp. 287-294, suitable photoinitiators are disclosed.

Specific examples of photoinitiators may include, without limitation, the following compounds or combinations thereof: benzophenone and substituted benzophenones, 1-hydroxycyclohexyl phenyl ketone, thioxanthones such as isopropylthioxanthone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-Benzyl-2-dimethylamino-(4-morpholinophenyl)butan-1-one, benzyl dimethyl ketal, bis-(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, 2,4,6- Trimethylbenzoyldiphenylphosphine, 2,4,6-trimethoxybenzoyldiphenylphosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one or 5,7-diiodo-3-butoxy-6-fluorone.

Suitable commercially available photoinitiators include Irgacure™ 184, Irgacure™ 500, Irgacure™ 369, Irgacure™ 1700, Irgacure™ 651, Irgacure™ 1000, Irgacure™ 1300, Irgacure™ 1870, Irgacure™ 2959, Darocur™ 1173, Darocur™4265 and Darocur™ ITX, available from BASF AG, Lucerin™ TPO, available from BASF AG, Esacure™ KT046, Esacure™ KIP150, Esacure™ KT37 and Esacure™ EDB, available in L ^a M ^b ERTI, H-NuTM 470 and H-Nu™ 470X, available from SPECTRA GROUP Ltd.

Preferred photoinitiators contain one or more photoinitiator functional groups derived from a Norrish I-type photoinitiator selected from the group consisting of benzoin ethers, benzyl ketals, α,α-dialkoxyacetophenones, α-hydroxyalkylphenones, α-aminoalkylphenones, acylphosphine oxides, acylphosphine sulfides, α- haloketones, a-halosulfones and phenylglyoxalates.

Preferred photoinitiators contain one or more photoinitiator functional groups derived from a Norrish II-type initiator selected from the group consisting of benzophenones, thioxanthones, 1,2-diketones, and anthraquinones.

In a particularly preferred embodiment of the UV curable inkjet composition or ink, a combination of an acylphosphine oxide photoinitiator and a thioxanthone photoinitiator is used, preferably a polymeric or polymerizable thioxanthone photoinitiator, more preferably a thioxanthone photoinitiator. polymerizable. With the latter photoinitiator a low viscosity can be achieved.

Other suitable diffusion-hindered photoinitiators are those described in EP 2065362 A (AGFA) and EP 2161264 A (AGFA).

In a photoinitiator system, one of the photoinitiators may also act as a sensitizer to enhance the reactivity of another photoinitiator. Preferred sensitizers are polymerizable sensitizers such as those disclosed in EP 2053095 A (FUJIFILM).

In order to further increase photosensitivity, the UV curable inkjet ink or composition may further contain co-initiators. Suitable examples of these coinitiators can be categorized into three groups: (1) tertiary aliphatic amines such as methyldiethanolamine, dimethylethanolamine, triethanolamine, triethylamine, and N-methylmorpholine, (2) aromatic amines such as amylparadimethylaminobenzoate, 2-n-butoxyethyl-4-(dimethylamino )benzoate, 2-(dimethylamino)ethylbenzoate, ethyl-4-(dimethylamino)benzoate, and 2-ethylhexyl-4-(dimethylamino)benzoate, and (3) (meth)acrylated amines such as dialkylamino alkyl(meth)acrylates (for example diethylaminoethyl acrylate) or N-morpholinoalkyl-(meth)acrylates (eg N-morpholinoethyl acrylate). Aminobenzoates are preferred as coinitiators. When one or more of these co-initiators are included in the UV-curable (jet) ink or composition, amounts that do not cause health risks are used.

A combination of a tertiary amine-containing polymerizable co-initiator and a tertiary amine-containing polymeric co-initiator may be advantageously used in order to adjust the viscosity of the UV curable inkjet ink.

Ethylhexyl-4-dimethylaminobenzoate (EHA) is preferably present in the radiation-curable (jet) ink or composition in an amount of 0.5 wt% to 5.0 wt%, more preferably in an amount of 1.0 wt% to 4.0 wt% and most preferably 3 wt% or less, wherein all weight percentages (wt%) are based on the total weight of the composition or (jet) ink curable by UV radiation.

Said at least one tertiary amine coinitiator may also be a polymerizable coinitiator containing a tertiary amine, more preferably a polymerizable coinitiator containing one or more 4-dialkylaminobenzoate groups, most preferably a polymerizable coinitiator containing one or more 4-dimethylaminobenzoate groups. . Other preferred tertiary amine groups for said at least one polymerizable coinitiator containing a tertiary amine include aliphatic tertiary amine groups and piperazine groups.

The UV radiation curable (injection) composition or ink according to the present invention preferably contains the polymerizable co-initiator containing a tertiary amine in an amount of 1.0 wt% to 10.0 wt%, more preferably 2.0 wt% to 7.0 wt% and most preferably from 3.0 wt% to 5.0 wt%, wherein all weight percentages (wt%) are based on the total weight of the composition or (injection) ink curable by UV radiation.

Said at least one tertiary amine coinitiator may also be a polymeric coinitiator containing a tertiary amine, more preferably a polymeric coinitiator containing one or more 4-dialkylaminobenzoate groups, most preferably a polymeric coinitiator containing one or more 4-dimethylaminobenzoate groups. . Other preferred tertiary amine groups for said at least one polymeric coinitiator containing a tertiary amine include aliphatic tertiary amine groups and piperazine groups.

In a preferred embodiment, said at least one tertiary amine-containing polymeric coinitiator is a polyether-based polymer. Particularly preferred polymeric coinitiators are derivatives of ethoxylated trimethylolpropane, propoxylated trimethylolpropane, polyethylene oxide, polypropylene oxide, ethoxylated neopentyl glycol, propoxylated neopentyl glycol, copolymers of polyethylene oxide and propylene oxide, ethoxylated glycerol, propoxylated glycerol, ethoxylated pentaerythritol, propoxylated pentaerythritol, and polytetrahydrofuran. .

In another preferred embodiment, said at least one tertiary amine-containing polymeric coinitiator has a number average molecular weight of no more than 1500, more preferably no more than 1000, and most preferably no more than 750.

In a particularly preferred embodiment, the tertiary amine-containing polymeric coinitiator is selected from the group consisting of:

wherein the compound has a number average molecular weight of not more than 1500 or wherein n is an integer from 1 to 4.

Suitable corresponding polymeric coinitiators containing a tertiary amine are commercially available under the trade names Omnipol™ ASA (CASRN71512-90-8) from IGM Resins, Genopol™ AB-1 and AB-2 (CASRN1215019-68-3) from RAHN. , and Speedcure™ 7040 (CASRN1182751-31-0) from LAMBSON.

Preferred polymeric coinitiators containing a tertiary amine are polymeric coinitiators having a dendritic polymeric architecture, more preferably a hyperbranched polymeric architecture. Preferred hyperbranched polymeric coinitiators are disclosed in US 2006014848 (AGFA).

The UV radiation curable (injection) composition or ink preferably includes the co-initiator in an amount between 0.1% by weight and 30.0% by weight, more preferably in an amount between 0.5% by weight and 10.0% by weight, most preferably in an amount between 1.0% by weight and 5.0% by weight with respect to the total weight of the composition or inkjet ink curable by UV radiation.

Preferably, the UV curable (injection) ink or composition does not include a photoinitiator selected from the group consisting of 2-hydroxy-2-methylpropiophenone, benzophenone, 2-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 1-Hydroxycyclohexylphenylketone, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, 4-isopropyl-9H-thioxanthen-9-one, 2-isopropyl-9H-thioxanthen-9 -one and 2,4-diethyl-9H-thioxanthen-9-one. Such a UV-curable composition or ink (jet) does not have an uncertain toxicology.

polymerizable compounds

Any polymerizable compound commonly known in the art can be used. The polymerizable compound can be any monomer and/or oligomer found in "Polymer Handbook Vol 1 2, 4th edition, edited by J. BRANDRUP et al., Wiley-Interscience, 1999. An oligomer in the present invention is understood to contain 2 to 8 repeating monomeric units.

In a UV curable (jet) ink or composition containing a substantial amount of water and/or organic solvents, the polymerizable compound may also be a crosslinkable copolymer. In a hybrid inkjet ink, the crosslinkable polymer is preferably present as a polymeric particle, for example as a latex, preferably an acrylate-based latex or a polyurethane-based latex.

A free radically polymerizable monomer or oligomer is preferably used as the polymerizable compound. A combination of monomers, oligomers and/or prepolymers can also be used. The monomers, oligomers, and/or prepolymers may possess different degrees of functionality, and a mixture including combinations of mono-, di-, or tri-functional and higher polymerizable functionality monomers, oligomers, and/or prepolymers may be used. The viscosity of UV-curable (injection) inks and compositions can be adjusted by varying the ratio of monomers to oligomers.

Preferred monomers and oligomers are those listed in paragraphs [0106] to [0115] of EP 1911814 A (AGFA).

A monofunctional polymerizable compound is generally used to improve the flexibility of a cured layer, while a polyfunctional polymerizable compound is used to improve the scratch resistance of the cured layer.

A monofunctional polymerizable compound contains a single polymerizable group, preferably a free radical polymerizable group selected from the group consisting of an acrylate, a methacrylate, an acrylamide, a methacrylamide, a styrene group, a maleate, a fumarate, an itaconate, a vinyl ether, a vinyl ester, an allyl ether and an allyl ester.

In a preferred embodiment, the monofunctional polymerizable compounds are selected from acrylic acid, methacrylic acid, maleic acid (or its salts), maleic anhydride, alkyl (meth)acrylates (linear, branched and cycloalkyl) such as (meth)acrylate methyl, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, aryl (meth)acrylates such as (meth)acrylate benzyl, and phenyl (meth)acrylate, hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate, (meth)acrylates with other types of functionalities (for example, substituted with oxiranes , amino, fluoro, polyethylene oxide, phosphate) such as glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, trifluoroethyl acrylate, methoxy polyethylene glycol (meth)acrylate, and tripropylene glycol phosphate (meth)acrylate, derived from allyl such as allyl glycidyl ether, styrenics such as such as styrene, 4-methylstyrene, 4-hydroxystyrene, 4-acetostyrene, and styrenesulfonic acid, (meth)acrylonitrile, (meth)acrylamides (including N-mono and N,N-disubstituted) such as N-benzyl (meth)acrylamide, maleimides such as N-phenyl maleimide, vinyl derivatives such as vinyl caprolactam, vinyl pyrrolidone, vinyl imidazole, vinyl naphthalene, and vinyl halides, vinyl ethers such as vinyl methyl ether, vinyl esters of carboxylic acids such as vinyl acetate, vinyl butyrate and vinyl benzoate. In a more preferred embodiment, the monofunctional polymerizable compounds are selected from monoacrylates and vinyllactams, such as N-vinylcaprolactam. Particularly preferred monofunctional polymerizable compounds are selected from the group consisting of isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isoamylstyl acrylate, isostearyl acrylate, 2-ethylhexyl diglycol acrylate, 2-hydroxybutyl acid, 2-acryloyloxyethylhexahydrophthalic acid, butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-Hydroxypropyl, 2-Hydroxy-3-Phenoxypropyl Acrylate, Vinyl Ether Acrylate, 2-Acryloyloxyethylsuccinic Acid, 2-Acryloxyethylphthalic Acid, 2-Acryloxyethyl-2-hydroxyethyl-phthalic Acid, Lactone-Modified Flexible Acrylate, -Butylcyclohexyl Acrylate , caprolactone acrylate, cyclic trimethylolpropane formal acrylate, acryl cyclic trimethylolpropane to formal, ethoxylated nonyl phenol acrylate, isodecyl acrylate, isooctyl acrylate, octyldecyl acrylate, alkoxylated phenol acrylate, tridecyl acrylate, and acryloylmorpholine.

In a preferred embodiment, the monofunctional polymerizable compound is selected from monoacrylates and vinyllactams, such as N-vinylcaprolactam.

The N-vinyllactam is preferably a compound represented by Formula (A):

Formula (A),

wherein n represents an integer from 2 to 6, n is preferably an integer from 3 to 5 from the viewpoint of flexibility due to curing of the ink composition, adhesion to a substrate, and rapid availability of starting materials, n is more preferably 3 or 5, and n is particularly preferably 5, which is N-vinylcaprolactam. N-vinyl caprolactam is preferable, since it is easy to obtain at a relatively low price and results in particularly good ink curability and adhesion of a cured film to a recording medium.

The N-vinyllactam may have a substituent, such as an alkyl group or an aryl group, on the lactam ring and may have a saturated or unsaturated cyclic structure attached to the lactam ring. The compound represented by Formula (A) can be used alone or as a combination of two or more compounds.

For certain applications, limited or no monofunctional (meth)acrylates are used. For example, when the substrate is a textile worn directly on human skin, it can lead to skin sensitization. In such a case, the monomers and oligomers are preferably selected from a group comprising or consisting of vinyls, acrylamides, methacrylamides, vinyl carbonates, vinyl ethers, vinyl esters, vinyl carbamates, allyl ethers, allyl esters and their corresponding alkyne compounds. Polymerizable compounds including an allylic ether group, a vinylcarbonate group and an alkyne group are particularly preferred.

A polyfunctional polymerizable compound contains two, three or more polymerizable groups, preferably free radical polymerizable groups selected from the group consisting of an acrylate, a methacrylate, an acrylamide, a methacrylamide, a styrene group, a maleate, a fumarate, an itaconate , a vinyl ether, a vinyl ester, an allyl ether and an allyl ester.

In a preferred embodiment, the polyfunctional polymerizable compound is a bifunctional acrylate containing two polymerizable groups, ie two acrylate groups.

Preferred polyfunctional acrylates include triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1- ,9-nonanediol, neopentyl glycol diacrylate, dimethylol tricyclodecane diacrylate, bisphenol A EO (ethylene oxide) adduct diacrylate, bisphenol A OP (propylene oxide) adduct diacrylate, neopentyl glycol hydroxypivalate diacrylate, propoxylated neopentyl glycol diacrylate, diacrylate alkoxylated dimethyloltricyclodecane and polytetramethylene glycol diacrylate, trimethylolpropane triacrylate, EO modified trimethylolpropane triacrylate, tri(propylene glycol) triacrylate, caprolactone modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritoloxy tetraacrylate, hexa dipentaerythritol acrylate, ditrimethylolpropane tetraacrylate, glycerinpropoxy triacrylate and caprolactam modified dipentaerythritol hexaacrylate.

Other suitable difunctional acrylates include alkoxylated cyclohexanone dimethanol diacrylate, alkoxylated hexanediol diacrylate, dioxan glycol diacrylate, dioxan glycol diacrylate, cyclohexanone dimethanol diacrylate, diethylene glycol diacrylate, and neopentyl glycol diacrylate.

Other polyfunctional acrylates include propoxylated glycerin triacrylate and propoxylated trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, ethoxylated pentaerythritol tetraacrylate, methoxylated glycol acrylates, and acrylate esters.

Preferred polyfunctional acrylates include dipropylene glycol diacrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, cyclohexanone dimethanol diacrylate, polyethylene glycol 200 diacrylate, 3-methyl-1,5-pentanediol diacrylate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate and dipentaerythritol pentaacrylate.

The polyfunctional polymerizable compound may have two different polymerizable groups, such as a vinyl ether group and an acrylate group. Preferred vinyl ether acrylates are those disclosed in US 6310115 (AGFA). A particularly preferred compound is 2-(2-vinyloxyethoxy)ethyl acrylate (VEEA). Other suitable vinyl ether acrylates are those described in columns 3 and 4 of US 6767980 B (NIPPON SHOKUBAI).

Instead of difunctional or polyfunctional acrylates, their methacrylate analogs can also be used.

The UV radiation curable (injection) composition or ink preferably contains at least one monomer comprising at least one vinyl ether group and at least one polymerizable group selected from the group consisting of an acrylate group and a methacrylate group, wherein this monomer is preferably represented by Formula (B):

Formula (B),

in which:

R5 represents a hydrogen atom or a methyl group, and

n represents an integer from 0 to 4. Most preferably, R5 represents a hydrogen atom. Such a monomer retards the vitrification of the polymerizing network during UV curing, which reduces the amount of monomers that can migrate.

In a preferred embodiment, said at least one monomer comprising at least one vinyl ether group and at least one (meth)acrylate group is preferably selected from the group consisting of:

In the most preferred embodiment of the UV radiation curable (jet) ink or composition, said at least one monomer comprising at least one vinyl ether group and at least one polymerizable group selected from the group consisting of an acrylate group and a methacrylate group is 2-(2'-vinyloxyethoxy)ethyl acrylate.

Other suitable vinyl ether (meth)acrylates are those described in columns 3 and 4 of US 6767980 B (NIPPON SHOKUBAI).

A single compound or a mixture of vinyl ether acrylates can be used.

The UV radiation curable (injection) composition or ink according to the present invention contains at least 10% by weight, more preferably at least 20% by weight and most preferably at least 25% by weight of the monomer according to Formula (B), wherein all weight percentages (wt%) are based on the total weight of the UV curable (jet) ink or composition.

In a particularly preferred embodiment, the UV radiation curable inkjet ink includes a polymerizable composition consisting essentially of: a) 25-100% by weight of a monomer according to Formula (B), preferably 2-(2- vinyloxyethoxy)ethyl, b) 0-55% by weight of one or more polymerizable compounds X selected from the group consisting of monofunctional acrylates and difunctional acrylates, and c) 0-55% by weight of one or more polymerizable compounds Y selected from the group consisting of consists of trifunctional acrylates, tetrafunctional acrylates, pentafunctional acrylates and hexafunctional acrylates, with the proviso that if the weight percentage of compounds X is > 24% by weight, the weight percentage of compounds Y is > 1% by weight, and wherein all weight percentages are based on the total weight of the polymerizable composition.

dyes

The UV-curable (jet) ink may contain a colorant. The colorants used in curable inks can be dyes, pigments, or a combination thereof. Organic pigments and/or inorganic The colorant is preferably a polymeric pigment or dye, most preferably a color pigment.

The pigments may be black, white, cyan, magenta, yellow, red, orange, violet, blue, green, brown, mixtures thereof, and the like. This color pigment can be chosen from those described by HERBST, Willy, et al. Industrial Organic Pigments, Production, Properties, Applications. 3rd edition. Wiley-VCH, 2004. ISBN 3527305769.

Particular preferred pigments are C.I. Pigment Yellow 1,3, 10, 12, 13, 14, 17, 55, 65, 73, 74, 75, 83, 93, 97, 109, 111, 120, 128, 138, 139, 150, 151, 154, 155, 175, 180, 181, 185, 194 and 213.

Particular preferred pigments are C.I. Pigment Red 17, 22, 23, 41,48:1,48:2, 49:1,49:2, 52:1,57:1.88, 112, 122, 144, 146, 149, 170, 175, 176, 184, 185, 188, 202, 206, 207, 210, 216, 221,248, 251,254, 255, 264, 266, 270 and 272.

Particular preferred pigments are C.I. Pigment Violet 19, 23, 32 and 37.

Particular preferred pigments are C.I. Pigment Blue 15:1, 15:2, 15:3, 15:4, 15:6, 16, 56, 61 and aluminum phthalocyanine pigments (bridged).

Particular preferred pigments are C.I. Pigment Orange 5, 13, 16, 34, 40, 43, 59, 66, 67, 69, 71 and 73.

Particular preferred pigments are C.I. Pigment Green 7 and 36.

Particular preferred pigments are C.I. Pigment Brown 6 and 7.

Suitable pigments include mixed crystals of the particular preferred pigments mentioned above. Mixed crystals are also called solid solutions. For example, under certain conditions, different quinacridones mix with each other to form solid solutions, which are quite distinct from both physical mixtures of the compounds and from the compounds themselves. In a solid solution, the component molecules usually, but not always, enter the same crystal lattice as one of the components. The x-ray diffraction pattern of the resulting crystalline solid is characteristic of that solid and can be clearly distinguished from the pattern of a physical mixture of the same components in the same proportion. In such physical mixtures, it is possible to distinguish the x-ray pattern of each of the components, and the disappearance of many of its lines is one of the criteria for the formation of solid solutions. A commercially available example is Cinquasia™ Magenta RT-355-D, from BASF AG.

Carbon black is preferred as the black pigment. Suitable black pigments include carbon blacks such as Pigment Black 7 (for example Carbon Black MA8® from MITSUBISHI CHEMICAL), Regal® 400R, Mogul® L, Elftex® 320 from CABOT Co., or Carbon Black FW18, Special Black 250, Special Black 350, Special Black 550, Printex® 25, Printex® 35, Printex® 55, Printex® 90, Printex® 150T from DEGu Ss A. In a preferred embodiment, the carbon black pigment used is a pigment that comprises less than 0.15% extractable fraction by toluene using the method as described in section III, paragraph 5, of Resolution AP(89) 1 of September 13, 1989, published by the Council of Europe.

It is also possible to prepare mixtures of pigments. For example, in certain applications of inkjet printing, a neutral black inkjet ink is preferred, which can be obtained, for example, by mixing a black pigment and a cyan pigment in the ink. Pigments can also be combined to extend the color gamut ( gamut) in a set of inks. The inkjet application may also require one or more supplemental colors. Silver and gold are often desired colors to make a product more attractive, giving it an exclusive look.

The inks may also contain non-organic pigments. Suitable pigments are C.I. Pigment Metal 1,2 and 3. Illustrative examples of inorganic pigments include titanium oxide, barium sulfate, calcium carbonate, zinc oxide, lead sulfate, lead yellow, zinc yellow, iron(III) oxide red. , cadmium red, ultramarine blue, Prussian blue, chromium oxide green, cobalt green, amber, titanium black, and synthetic iron black. However, care must be taken to avoid migration and extraction of heavy metals in food application. Pigments containing a heavy metal selected from the group consisting of arsenic, lead, mercury and cadmium are not used in the preferred embodiment. In a more preferred embodiment, no inorganic pigments are used in the inkjet ink, with the exception of titanium oxide and calcium carbonate.

The pigment particles in the inkjet ink must be small enough to allow the ink to flow freely through the inkjet printing device, especially through the ejection nozzles. It is also recommended to use small particles to maximize color intensity and slow down sedimentation.

The number average size of the pigment particle is preferably between 0.050 and 1 µm, more preferably between 0.070 and 0.300 µm and particularly preferably between 0.080 and 0.200 µm. Most preferably, the number average size of the pigment particle does not exceed 0.150 pm. An average particle size of less than 0.050 pm is less desirable because of decreased light fastness, but mainly also because very small pigment particles or individual pigment molecules thereof still exhibit the possibility of extraction in food packaging applications.

The number average particle size of the pigment particles is best determined with a Brookhaven Instruments Particle Sizer BI90plus based on the principle of dynamic light scattering. The ink is diluted, for example, with ethyl acetate to a pigment concentration of 0.002% by weight. The BI90plus measurement settings are: 5 tests at 230C, angle 90°, wavelength 635nm and graphs = correction function.

In the case of a white UV-curable ink, a pigment with a refractive index greater than 1.60, preferably greater than 2.00, more preferably greater than 2.50, and most preferably greater than 2, is preferably used. 60. The white pigments can be used individually or in combination.

Titanium dioxide is preferably used for the pigment with a refractive index greater than 1.60. Titanium oxide occurs in the crystalline forms of the anatase type, the rutile type and the brookite type. The anatase type has a relatively low density and is easily ground into fine particles, while the rutile type has a relatively high refractive index and shows high coating ability. Any of these can be used in this invention. It is preferred to make the most possible use of the features and to make selections according to the use of the features. The use of the anatase type having low density and small particle size can achieve superior dispersion stability, ink storage stability and ejectability. At least two different crystal forms can be used in combination. The combined use of the anatase type and the rutile type, which has a high coloring power, can reduce the total amount of titanium oxide, leading to improved storage stability and ink ejection performance.

For the surface treatment of titanium oxide, aqueous treatment or gas phase treatment is applied, and an alumina-silica treating agent is usually employed. Titanium oxide untreated, or treated with alumina or treated with alumina and silica can be used.

The number average particle diameter of the titanium oxide or other white pigments is preferably between 50 and 500 nm, more preferably between 150 and 400 nm and most preferably between 200 and 350 nm. Sufficient covering power cannot be obtained when the average diameter is less than 50nm, and the storage capacity and ejection suitability of the ink tend to degrade when the average diameter exceeds 500nm. Determination of the number average particle diameter is most conveniently performed by photon correlation spectroscopy at a wavelength of 633 nm using a 4 mW HeNe laser on a diluted sample of the pigmented inkjet ink. The appropriate Malvern™ nano-S particle size analyzer, available from Goffin-Meyvis, was used. To prepare a sample, for example, a drop of ink can be added to a cuvette containing 1.5 ml of ethyl acetate and mixed until a homogeneous sample is obtained. The measured particle size is the mean value of 3 consecutive measurements, consisting of 6 trials of 20 seconds.

Pigments are generally stabilized in the dispersion medium using dispersing agents, such as dispersants or polymeric surfactants. However, the surface of the pigments can be modified to obtain so-called "self-dispersible" or "self-dispersing" pigments, ie pigments that are dispersible in the dispersion medium without dispersants.

The pigment is preferably used in a pigment dispersion used to prepare inkjet inks in an amount of 10 to 40% by weight, more preferably 15 to 30% by weight based on the total weight of the pigment dispersion. In a curable inkjet ink, the pigment is preferably present in an amount of 0.1 to 20% by weight, preferably 1 to 10% by weight, based on the total weight of the inkjet ink.

polymeric dispersants

Typical polymeric dispersants are copolymers of two monomers, but may contain three, four, five, or even more monomers. The properties of polymeric dispersants depend on both the nature of the monomers and their distribution in the polymer. Preferably, the copolymeric dispersants have the following polymer compositions:

• statistically polymerized monomers (for example, monomers A and B polymerized in ABABAABAB), • monomers polymerized according to an alternating order (for example, monomers A and B polymerized in ABABAABAB),

• gradient polymerized (tapered) monomers (for example, monomers A and B polymerized in AAABAABBABBB),

• block copolymers (for example, monomers A and B polymerized in AAAAABBBBBB) in which the length of block of each of the blocks (2, 3, 4, 5 or even more) is important for the dispersion capacity of the polymeric dispersant,

• graft copolymers (graft copolymers consisting of a polymeric backbone with polymeric side chains attached to the main chain), and

• Mixed forms of these polymers, such as gradient block copolymers.

A list of dispersants is shown in the "Dispersants" section, more specifically in paragraphs [0064] to [0070] and [0074] to [0077] of EP 1911814 A (AGFA GRAPHICS), incorporated herein by specific reference. suitable polymeric dispersants.

The polymeric dispersant preferably has a number average molecular weight Mn of between 500 and 30,000, more preferably between 1,500 and 10,000.

The polymeric dispersant preferably has a weight average molecular weight Mw of less than 100,000, more preferably less than 50,000 and most preferably less than 30,000.

The polymeric dispersant preferably has a polymeric dispersity DP of less than 2, more preferably less than 1.75, and most preferably less than 1.5.

The following are commercial examples of polymeric dispersants:

DISPERBYK™ dispersants, available from BYK CHEMIE GMBH,

SOLSPERSE™ dispersants, available through LUBRIZOL,

dispersants TEGO™ DISPERS™ from EVONIK,

EDAPLAN™ dispersants from MÜNZING CHEMIE,

LYONDELL ETHACRYL™ dispersants,

ISP's GANEX™™ dispersants,

DISPEX™ and EFKA™ dispersants from BASF,

DISPONER™ dispersants from DEUCHEM.

Particularly preferred polymeric dispersants include Solsperse™ dispersants from LUBRIZOL, Efka™ dispersants from B ^to S ^f , and Disperbyk™ dispersants from BYK CHEMIE GMBH. Particularly preferred dispersants are Solsperse™ 32000, 35000 and 39000, from LUBRIZOL.

The polymeric dispersant is preferably used in an amount of 2 to 600% by weight, more preferably 5 to 200% by weight, and most preferably 50 to 90% by weight relative to the weight of the pigment.

Dispersion Synergists

A dispersion synergist is usually made up of an anionic part and a cationic part. The anionic part of the dispersion synergist shows a certain molecular similarity to the color pigment and the cationic part of the dispersion synergist is composed of one or more protons and/or cations that balance the charge of the anionic part of the dispersion synergist.

It is preferable to add the dispersion synergist in an amount less than that of the polymeric dispersant(s). The ratio of polymeric dispersant/dispersion synergist is pigment dependent and should be determined experimentally. Typically, the ratio of weight percent polymeric dispersant/weight percent dispersion synergist is set between 2:1 and 100:1, preferably between 2:1 and 20:1.

Some suitable commercially available dispersion synergists include Solsperse™ 5000 and Solsperse™ 22000, from LUBRIZOL.

Particularly preferred pigments for the magenta ink used are a diketopyrrolopyrrole pigment or a quinacridone pigment. Suitable dispersion synergists include those disclosed in EP 1790698 A (AGFA GRAPHICS), EP 1790696 A (AGFA GRAPHICS), WO 2007/060255 (AGFA GRAPHICS) and EP 1790695 A (AGFA GRAPHICS).

In the Pigment Blue CI 15:3 pigment dispersion, the use of a sulfonated Cuphthalocyanine dispersion synergist, such as Solsperse™ 5000 from LUBRIZOL, is preferred. Suitable dispersion synergists for yellow inkjet inks include those disclosed in EP 1790697 A (AGFA GRAPHICS).

polymerization inhibitors

The UV curable (jet) ink or composition may contain a polymerization inhibitor. Suitable polymerization inhibitors include phenol-type antioxidants, hindered amine light stabilizers, phosphorus-type antioxidants, and hydroquinone monomethyl ether commonly used in (meth)acrylate monomers. Hydroquinone, t-butylcatechol, and pyrogallol can also be used.

Suitable commercial inhibitors are, for example, Sumilizer™ GA-80, Sumilizer™ GM and Sumilizer™ GS, manufactured by Sumitomo Chemical Co. Ltd., Genorad™ 16, Genorad™ 18 and Genorad™ 20 from Rahn AG, Irgastab™ UV10 and Irgastab™ UV22, Tinuvin™ 460 and CGS20 from BASF, Floorstab™ UV range (UV-1, UV-2, UV-5 and UV-8) from Kromachem Ltd, Additol™ S range (S100, S110, S120 and S130) from Cytec Surface Specialties.

Since excessive addition of these polymerization inhibitors will reduce the sensitivity of the ink to curing, it is preferable that the amount capable of preventing polymerization be determined before mixing. Preferably, the amount of a polymerization inhibitor is less than 2% by weight with respect to the total weight of the composition or inkjet ink curable by UV radiation.

In a preferred embodiment, the polymerization inhibitor is a polymerizable inhibitor, preferably containing one or more acrylate groups to obtain good reactivity.

Surfactants

The UV curable (injection) composition or ink may contain at least one surfactant. The surfactant can be anionic, cationic, non-ionic or zwitterionic and is preferably added in a total quantity of less than 3% by weight with respect to the total weight of the ink and, particularly, in a total quantity of less than 1% by weight with respect to the ink. to the total weight of the UV-curable composition or inkjet ink.

Preferred surfactants are selected from fluorine surfactants (such as fluorinated hydrocarbons) and silicone surfactants. Silicone surfactants are preferably siloxanes and may be alkoxylated, polyester-modified, polyether-modified, hydroxy-functional polyether-modified, amine-modified, epoxy-modified, and other modifications or combinations thereof. Preferred siloxanes are polymeric, for example polydimethylsiloxanes.

Preferred silicone surfactants include BYK™ 333 and BYK™ UV3510 from BYK Chemie.

In a preferred embodiment, the surfactant is a polymerizable compound.

Preferred polymerizable silicone surfactants include a (meth)acrylated silicone surfactant. Most preferably, the (meth)acrylated silicone surfactant is an acrylated silicone surfactant, because acrylates are more reactive than methacrylates.

In a preferred embodiment, the (meth)acrylated silicone surfactant is a polyether-modified (meth)acrylated polydimethylsiloxane or a polyester-modified (meth)acrylated polydimethylsiloxane.

Preferred commercially available (meth)acrylated silicone surfactants include Ebecryl™ 350, a silicone diacrylate from Cytec, BYK™ UV3500 and BYK™ UV3530 polyether-modified acrylated polydimethylsiloxane, BYK™ UV3570 polyester-modified acrylated polydimethylsiloxane, all produced by BYK Chemie, TegoTM Rad 2100, TegoTM Rad 2200N, TegoTM Rad 2250N, TegoTM Rad 2300, TegoTM Rad 2500, TegoTM Rad 2600 and TegoTM Rad 2700, TegoTM RC711 by EVONIK, SilaplaneTM FM7711, SilaplaneTM FM7721, SilaplaneTM FM1071, SilaplaneTM FM7731 Silaplane™ FM0721, Silaplane™ FM0725, Silaplane™ TM0701 and Silaplane™ TM0701T, all produced by CHISSO Corporation, and DMS-R05, DMS-R11, DMS-R18, DMS-R22, DMS-R31, DMS-U21, DBE-U22 , SIB1400, RMS-044, RMS-033, RMS-083, UMS-182, UMS-992, UCS-052, RTT-1011 and UTT-1012, all produced by Gelest, Inc..

Preparation of inkjet inks curable by UV radiation

The preparation of pigmented UV curable inkjet inks is commonly known to those skilled in the art. Preferred preparation methods are disclosed in paragraphs [0076] to [0085] of WO 2011/069943 (AGFA).

Inkjet Printing Procedures

Another aspect of our invention is an inkjet printing process that includes the steps of: a) applying a UV-curable composition as defined above onto a substrate and b) UV-curing the UV-curable composition onto the substrate. .

The UV curable composition can be applied as a primer or varnish using an inkjet technique or another printing technique, such as flexographic printing, offset printing or screen printing, or a coating technique.

In a preferred embodiment of the inkjet printing process, the UV curable composition is applied by ejecting a UV curable inkjet ink onto the substrate.

The UV radiation curable inkjet ink including a photoinitiator according to the invention is advantageously used to obtain a printed article for interior decoration. However, UV curable inkjet ink is also suitable for other purposes such as printing on signs, banners, and inkjet printed packaging for food and pharmaceutical items.

In a preferred embodiment of the inkjet printing process, the UV radiation curing is carried out by UV LED curing.

A preferred inkjet printing process comprises the steps of: a) jetting a UV-curable inkjet ink according to the invention onto a substrate, and b) at least partially UV-curing the radiation-curable inkjet ink UV on the substrate with UV LEDs, preferably UV LEDs having an emission wavelength greater than 360nm.

In a preferred embodiment, the UV curable inkjet ink is printed in a single pass printing operation.

In a preferred embodiment, the UV curable inkjet ink is cured by UV LED radiation within 5 seconds of being printed.

In a preferred embodiment, the dose of UV radiation used to cure UV curable inkjet inks is less than 300 mJ/cm2.

With the inkjet printing process, a printed article is obtained. A preferred printed article includes a substrate and the UV curable inkjet ink as described above. The substrate is preferably selected from the group consisting of plastic, metal, textiles, leather, and glass.

inkjet printing devices

UV curable inkjet ink can be ejected by one or more printheads, ejecting small droplets of ink in a controlled manner through nozzles onto a substrate, which is moving relative to the printhead(s).

A preferred printhead for the inkjet printing system is a piezoelectric printhead. Piezoelectric inkjet printing is based on the movement of a piezoelectric ceramic transducer by applying voltage to it. As voltage is applied, the shape of the printhead's piezoelectric ceramic transducer changes, forming a cavity that is then filled with ink. When the voltage is switched off again, the ceramic expands and returns to its original shape by ejecting a drop of ink from the print head. However, the inkjet printing method according to the present invention is not limited to piezoelectric inkjet printing. Other types of inkjet print heads can be used, such as continuous type heads.

The ink jet print head normally moves back and forth in a transverse direction across the moving ink-receiving surface. Often the inkjet print head does not print on its way back. Bi-directional printing, also called multi-pass printing, is preferred for high area throughput. Another preferred printing method is by a "single-pass printing process," which can be accomplished using page-width inkjet printheads or multiple, staggered, full-width inkjet printheads. from that of the ink-receiving surface. In a single pass printing process, the inkjet printheads normally remain stationary and the substrate surface is transported under the inkjet printheads.

curing devices

UV curable compositions, inks or inkjet inks according to the present invention are cured by exposing them to ultraviolet radiation.

In inkjet printing, the curing medium can be arranged next to the inkjet printer's print head so that it moves with it and that the curing radiation is applied very shortly after jet application. Such rapid curing is often referred to as "intermediate curing" and is used to improve image quality by controlling the point size. Preferably, such curing means is comprised of one or more UV LED lamps. In this configuration, it can be difficult to provide other types of curing media that are small enough to be connected to the print head and able to move with it. Therefore, a fixed radiation source can be used, for example a UV curing radiation source, connected to the radiation source through a flexible radiation conductive medium, such as a fiber optic cable bundle or a flexible tube with internal reflection. Alternatively, actinic radiation may be supplied from a fixed source to the radiation head, by an arrangement of mirrors, including a mirror on the print head.

The radiation source may also be an elongated radiation source which extends transversely across the substrate to be cured and which may be adjacent to the transverse path of the printhead such that subsequent rows of images formed by the printhead are they pass, step by step or continuously, under said radiation source.

Any source of ultraviolet light, as long as part of the emitted light can be absorbed by the photoinitiator or photoinitiator system, can be used as a radiation source, such as a high or low pressure mercury lamp, a cold cathode tube, a black light, an ultraviolet LED, an ultraviolet laser and a flashing light. Of these, the preferred source is one that exhibits a relatively long wavelength UV contribution having a dominant wavelength of 300-400 nm. Specifically, a UV-A light source is preferred due to reduced light scattering therefrom, resulting in more efficient interior curing.

UV radiation is usually classified as UV-A, UV-B, and UV-C based on the following parameters:

• UV-A: 400nm to 320nm

• UV-B: 320nm to 290nm

• UV-C: from 290nm to 100nm.

In a preferred embodiment, the inkjet printing device comprises one or more UV LEDs with a wavelength greater than 360 nm, preferably one or more UV LEDs with a wavelength greater than 380 nm and most preferably UV LEDs. of a wavelength of about 395 nm.

Likewise, it is possible to cure the image using, consecutively or simultaneously, two light sources with different wavelengths or illuminances. For example, a UV-C rich first UV source can be selected which is particularly in the range of 260nm to 200nm. The second UV source can be rich in UV-A, such as a gallium-doped lamp or a different lamp whose light is rich in UV-A and UV-B. The use of two UV sources has proven to be advantageous in offering, for example, a high speed of cure and a high degree of cure.

To facilitate curing, the inkjet printing device often includes one or more oxygen reduction units. Oxygen reduction units place a blanket of nitrogen or other relatively inert gas (eg CO2) with adjustable position and variable inert gas concentration to reduce the oxygen concentration in the curing environment. Residual oxygen levels are typically kept as low as 200ppm, although they generally remain in the range of 200ppm to 1200ppm.

industrial applicability

There are no real restrictions on the type of substrate. Substrates may have ceramic, metal, wood, paper, or polymeric surfaces for printing. The substrate can also be provided with a primer, e.g. with a white primer or ink.

The compositions, inks or inkjet inks curable by UV radiation including a photoinitiator according to the invention are advantageously used to obtain a printed article for interior decoration.

However, the UV curable compositions, inks or inkjet inks are also suitable for other purposes such as printing on signs, banners and printed (inkjet) packaging for food and pharmaceutical items.

It is understood that food packaging also includes the packaging of liquids and beverages such as milk, water, colas, beer, vegetable oils and the like.

The invention is advantageously used to provide food packaging, especially 'primary' food packaging. A primary food packaging is the material with which the product is first surrounded and held. Typically, it is the smallest unit of distribution or use and is the package that is in direct contact with the contents. Of course, UV curable inkjet inks and compositions can also be used in secondary and tertiary packaging for food safety reasons. A secondary container is outside of the primary container, and may be used to group primary packages together. Tertiary packaging is used for the handling of bulk products, storage in warehouses and shipment in means of transport. The most common form of tertiary packaging is a unit load with which a container can be well filled.

The substrate may be porous, such as e.g. eg textile, paper and board substrates, or substantially non-absorbent substrates such as e.g. eg a substrate having a polyethylene terephthalate surface.

Preferred substrates include polyethylene, polypropylene, polycarbonate, polyvinyl chloride surfaces, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polylactide (PLA), and polyimide. The substrate may also be a paper substrate, such as plain paper or resin-coated paper, e.g. eg polyethylene or polypropylene coated paper. There are no real restrictions on the type of paper and it includes wallpaper, but also heavier paper, often referred to as paperboard, such as coated paperboard, corrugated board and packing board.

Substrates can be transparent, translucent or opaque. Preferred opaque substrates include so-called synthetic paper, such as those from Agfa-Gevaert's Synaps™ range, which are an opaque sheet of polyethylene terephthalate having a density of 1.10 g/cm 3 or greater.

There are no restrictions on the shape of the substrate. It may be a flat sheet, such as a sheet of paper or polymeric film, or it may be a three-dimensional object such as furniture, lamps, and other printed items for interior decoration suitable for printing.

In a preferred embodiment, the substrate is a decorated panel selected from the group consisting of kitchen panels, floor panels, furniture panels, ceiling panels and wall panels. The preferred decorative panels are known as LVT ( Luxury Vinyl Tile).

A preferred decoration is a wood pattern or wood grain. Preferred inkjet printing methods according to the present invention include:

• decorative printing of wood patterns on undecorated substrates to enhance the decorative function, eg.

eg in combination with natural wood decor or in combination with other types of printed decor materials (e.g. printed decor paper-based laminates),

• the printing of side strips for furniture that are preferably made of ABS,

• printing of wood patterns on non-wood substrates (optionally in combination with natural wood),

• printing of wood patterns on cheap substrates (chipboard,...),

• printing of wood patterns on durable materials (metal panels, MDF panels, HDF panels), and

• printing of wood patterns on floors, furniture materials, ceilings, wall decoration, but also on objects (eg light switches), in order to obtain a decorative effect of undisturbed wood.

examples

Materials

TPO-L is ethylphenyl(2,4,6-trimethylbenzoyl) phosphinate, available under the name Omnirad™ TPO-L from IGM Resins BV.

THIOXANTONE-1 is a polymerizable thioxanthone having the chemical structure TX-1 and is a 50% by weight solution in VEEA. THIOXANTHONE-1 can be prepared according to Example 1 of EP 2684876 A (AGFA).

VEEA is 2-(2'-vinyloxyethoxy)ethyl acrylate, a difunctional monomer, available from NIPPON SHOKUBAI, Japan. GAB1 is a polymeric 4-dimethylaminobenzoic acid derivative, available under the name GENOPOL™ AB1 from Rahn.

INHIB is a mixture that forms a polymerization inhibitor having a composition according to Table 3.

Table 3

Cupferron™ AL is aluminum N-nitrosophenylhydroxylamine from WAKO CHEMICALS LTD.

PET175 is a 175 µm thick polyethylene terephthalate film (not provided with an adhesive layer), available under the trade name Astera™ of type U175.332 from AGFA-GEVAERT NV.

Methods

1. FTA

Molecular mass was determined by TLC-MS, according to the following procedure. TLC was performed under the circumstances indicated in the examples with synthetics. The TLC chromatogram was analyzed using a CAMAG TLC-MS interface coupled to an AmaZon SL mass spectrometer (provided by Brüker Daltonics) through an Agilent 1100 HPLC pump. First, a blank spectrum was obtained by eluting a point of the TLC plate in which no compounds were present with a 0.01 molar solution of ammonium acetate in methanol. A second spectrum of the compound to be analyzed was obtained by eluting the point of the compound under examination with a 0.01 molar solution of ammonium acetate in methanol. The first spectrum was subtracted from the second, which gave the spectrum of the compound to be analyzed.

2. Viscosity

The viscosity of the UV curable compositions was measured at 45°C and a shear rate of 1,000 s-1 with a HAAKE Rotovisco™ RV1 viscometer.

Example 1

This example illustrates the synthesis of an acylphosphine oxide initiator in which the acyl group is a 2,4,6-trimethylbenzoyl group substituted in position 3 by an oxalylamide group.

Synthesis

The synthesis is carried out in steps 1 to 6.

Step 1: Synthesis of Compound C-2

100 g (0.6 mol) of 2,4,6-trimethylbenzoic acid (compound C-1) was added to 2.79 kg of nitric acid (65% by weight). 116.6 ml of concentrated sulfuric acid were then added and the mixture was stirred for 18 hours at room temperature. The mixture was added to 1.5 kg of an ice/water mixture. 2,4,6-trimethyl-3-nitrobenzoic acid (compound C-2) was precipitated from the medium. Compound C-2 was isolated by filtration and washed with water until neutral pH.

The isolated compound C-2 was dried to constant weight. 112 g of 2,4,6-trimethyl-3-nitrobenzoic acid were isolated (yield: 89%) (melting point 194°C (lit. 184°C Chemische Berichte, V120(5 ), P803-9 (1987))).

Step 2: Synthesis of Compound C-3

112 g (0.53 mol) of 2,4,6-trimethyl-3-nitrobenzoic acid were suspended in 1.2 L of toluene. 63.28 g (0.8 mol) of pyridine was added, followed by the addition of 95.18 g (0.8 mol) of thionyl chloride over 30 minutes. The temperature rose to 36°C during the addition. The reaction was allowed to continue for one hour at room temperature. Precipitated salts were removed by filtration and the solvent was evaporated under reduced pressure. 500 ml of t-butyl methyl ether were added and the mixture was again evaporated under reduced pressure. This process was repeated a second time. Thus, 119 g of 2,4,6-trimethyl-3-nitrobenzoyl chloride were isolated (yield: 99%). Compound C-3 was used in the next step without further purification.

Step 3: Synthesis of Compound C-4

Compound C-4 is (3-nitro-2,4,6-trimethylphenyl)-[ethoxy(phenyl)phosphoryl]methanone.

103.5 g (0.522 mol) of diethylphenylphosphonite were dissolved in 500 ml of toluene. The solution was heated up to 80°C. 119 g (0.52 mol) of compound C-3 was dissolved in 250 ml of toluene, and this solution was added to the mixture for 15 minutes. The reaction was allowed to continue for three hours at 80°C. The reaction was allowed to cool to room temperature and the mixture was extracted twice with 350 mL of saturated NaHCÜ3 solution and twice with 400 mL of brine. The organic fraction was isolated, dried over Na2S04 and evaporated under reduced pressure. The crude compound C-4 was purified by preparative column chromatography on a Graceresolve RS80 column using methylene chloride as eluent. 88 g of compound C-4 were isolated (yield: 47%). (TLC analysis on TLC Silica gel 60F254 supplied by Merck, eluant methylene chloride/ethyl acetate 90/10: Rf: 0.49). Molecular mass was confirmed using the TLC-MS methodology described above.

Step 4: Synthesis of Compound C-5

Compound C-5 is (3-amino-2,4,6-trimethylphenyl)-[ethoxy(phenyl)phosphoryl]methanone

24.3 g (70 mmol) of compound C-4 were dissolved in 200 g of methanol. 1 g of RaNi was washed three times with methanol and added to the reaction mixture. Compound C-4 was hydrogenated at 30°C and 50 bar hydrogen pressure. A Once the hydrogenation was complete, the reaction mixture was allowed to cool to room temperature and the RaNi was removed by filtration. The solvent was removed under reduced pressure, and 21.6 g of compound C-5 was isolated (yield: 97.3%). Compound C-5 was used without further purification.

Step 5: Synthesis of Compound C-6

Compound C-6 is ethyl-2-[3-[ethoxy(phenyl)phosphoryl]carbonyl-2,4,6-trimethylanilino]-2-oxoacetate.

19.1 g (57.6 mmol) of compound C-5 were dissolved in 15 ml of methylene chloride. 8.19 g (63.4 mmol) of diisopropyl ethylamine were added and the mixture was cooled to 0°C. A solution of 8.65 g (63.4 mmol) of ethyloxalyl chloride in 30 ml of methylene chloride was added over 45 minutes, keeping the temperature at 0°C. The reaction mixture was allowed to continue for 16 hours at room temperature. The mixture was extracted twice with 100 ml of 2N hydrochloric acid solution, twice with 100 ml of saturated NaHCO3 solution and 100 ml of water. The organic fraction was dried over Na2SO4 and evaporated under reduced pressure. Crude compound C-6 was used without further purification.

Step 6: Synthesis of the OXA-1 compound

The OXA-1 compound is N-butyl-N'-[3-[ethoxy(phenyl)phosphoryl]-carbonyl-2,4,6-trimethylphenyl]oxamide.

10 g (theoretically 23 mmol) of compound C-6 were dissolved in 60 ml of acetonitrile. 8.41 g (0.115 mol) of butylamine were added and the mixture was heated under reflux for 4 hours. The solvent was removed under reduced pressure. Compound OXA-1 was purified by preparative column chromatography on a ProChrom LC80 column using Kromasil C18 100 A 10 gm as stationary phase and methanol/0.2 M ammonium acetate (70/30) as eluent. 0.87 g of compound OXA-1 was isolated (TLC analysis on Reveleris RP C18 TLC plates, supplied by Grace, eluant methanol/1M NaCl, Rf: 0.29). Molecular mass was confirmed using the TLC-MS methodology described above.

Example 2

This example illustrates the synthesis of the acylphosphine oxide initiator OXA-4.

Synthesis

3.02 g (7 mmol) of compound C-6 prepared in synthesis step 5 of Example 1 and 0.75 g (10 mmol) of 3-aminopropanol were dissolved in 20 ml of acetonitrile. The mixture was heated at reflux for 90 minutes. After 90 minutes the mixture was allowed to cool to room temperature and the solvent was removed under reduced pressure. Crude OXA-4 was purified by preparative column chromatography on a GraceResolve column using ethyl acetate as eluant. 2 g (yield: 62.5%) of OXA-4 were isolated (TLC analysis on Reveleris RP C18 TLC plates, supplied by Grace, eluant methanol/1M NaCl (70/30): Rf: 0.48). Molecular mass was confirmed using the TLC-MS methodology described above.

Example 3

This example illustrates the synthesis of a polymerizable acylphosphine oxide initiator according to the invention.

Synthesis

2.5 g (5.43 mmol) of the compound OXA-4 prepared in Example 2 was dissolved in 10 ml of ethyl acetate. 24 mg of BHT, 1.112 g (5.97 mmol) of 2-(2-vinyloxyethoxy)ethyl acrylate and 87 mg (0.55 mmol) of pyridine-3-sulfonic acid were added. The reaction mixture was heated to 70°C and the reaction was allowed to continue for 16 hours. An additional 0.1 g of 2-(2-vinyloxyethoxy)ethyl acrylate and 9 mg of pyridine-3-sulfonic acid were added and the reaction was allowed to continue for an additional 5 hours. The reaction mixture was allowed to cool to room temperature and the catalyst was removed by filtration. The solvent was removed under reduced pressure and compound OXA-6 was purified by preparative column chromatography on a GraceResolve column using methylene chloride/ethyl acetate (1/1) as eluant. 1.9 g (yield: 54%) of OXA-6 were isolated (TLC analysis on Reveleris RP C18 TLC plates supplied by Grace, eluent methanol/1M NaCl (70/30): Rf : 0.28). Molecular mass was confirmed using the TLC-MS methodology described above.

Example 4

This example illustrates the synthesis of a multifunctional acylphosphine oxide initiator according to the invention.

Synthesis

1.842 g (4 mmol) of the OXA-4 compound as prepared in Example 2 and 0.409 g (4.04 mmol) of triethylamine were dissolved in 40 ml of isopropyl acetate. A solution of 0.348 g (2 mmol) of glutaryl chloride in 10 ml of isopropyl acetate was added dropwise. The reaction was allowed to continue for three hours at room temperature and then refluxed for 90 minutes. Precipitated salts were removed by filtration and the solvent was removed under reduced pressure. OXA-13 was purified by preparative column chromatography on a GraceResolve column using ethyl acetate as eluant. 0.720 g (yield: 35.4%) of OXA-13 was isolated (TLC analysis on Reveleris RP C18 TLC plates supplied by Grace, eluant methanol/1M NaCl (75/25): Rf : 0.24). Molecular mass was confirmed using the TLC-MS methodology described above.

Example 5

This example illustrates the synthesis of an acylphosphine oxide initiator according to the invention, in which the acyl group is a 2,4,6-trimethylbenzoyl group substituted in position 3 by a urea group.

Synthesis

6.62 g (20 mmol) of compound C-5 as prepared in Example 1 was dissolved in 60 ml of methylene chloride. A solution of 3.8 g (30 mmol) of n.-hexyl isocyanate in 20 ml of methylene chloride was added and the reaction was allowed to continue for three hours at room temperature. The solvent was removed under reduced pressure and UREA-1 was isolated by preparative column chromatography on a GraceResolve RS80 column using gradient elution from 100% methylene chloride to 100% ethyl acetate. 5 g (y: 54%) of UREA-1 were isolated (TLC analysis on TLC Silicagel 60 F254, supplied by Merck, eluant 100% ethyl acetate, Rf: 0.27). UREA-1 was analyzed using 1H-NMR spectroscopy (DMSO d6).

Example 6

This example illustrates the synthesis of a polymerizable acylphosphine oxide initiator according to the invention, in which the acyl group is a 2,4,6-trimethylbenzoyl group substituted in position 3 by a urea group.

Synthesis

6.62 g (20 mmol) of compound C-5 as prepared in Example 1 was dissolved in 65 ml of methylene chloride. A solution of 2.96 g (21 mmol) of 2-acryloyloxyethyl acrylate was added and the reaction was allowed to continue for three hours at room temperature. An additional 1.48 g (10.5 mmol) of 2-acryloyloxyethyl acrylate was added and the reaction was allowed to continue at room temperature for 16 hours. The solvent was removed under reduced pressure. UREA-2 was isolated by preparative column chromatography on a Prochrom LC80 column using Kromasil C18 100A 10 pm as stationary phase and methanol/0.2M ammonium acetate (60/40) as eluant. 3.87 g (y: 41%) of UREA-2 were isolated (TLC analysis on Reveleris RP C18 TLC plates, supplied by Grace, methanol/1M NaCl (60/40) as eluant, Rf: 0.16). ^u R ^e A-2 was analyzed using 1 H-NMR spectroscopy (DMSO d6, 50 µl trifluoroacetic acid in 0.7 ml DMSO d6).

Example 7

This example illustrates the synthesis of a multifunctional acylphosphine oxide initiator according to the invention, in which the acyl group is a 2,4,6-trimethylbenzoyl group substituted in position 3 by a urea group.

7.28 g (22 mmol) of compound C-5 as prepared in Example 1 was dissolved in 60 ml of methylene chloride. A solution of 1.68 g (10 mmol) of hexamethylene diisocyanate in 20 ml of methylene chloride was added and the reaction was allowed to continue at room temperature for 24 hours. Solvent was removed under reduced pressure and UREA-3 was isolated by preparative column chromatography on a Prochrom LC80 column using Kromasil C18 100A 10 pm as stationary phase and methanol/0.2M ammonium acetate (70/30) as eluent. 1.94 g (y: 21%) of UREA-3 was isolated (TLC analysis on Reveleris RP C18 TLC plates, supplied by Grace, methanol/1M NaCl (80/20) as eluent, Rf: 0.42). UREA-2 was analyzed using 1 H-NMR spectroscopy (DMSO d6, 50 µl trifluoroacetic acid in 0.7 ml DMSO d6).

Example 8

This example illustrates malodour reduction of UV-curable compositions containing an acylphosphine oxide initiator according to the invention.

Preparation of compositions curable by UV radiation

Comparative Example COMP-1 and Inventive Examples INV-1 through INV-7 were prepared according to Table 4. Weight percentages (wt%) are based on the total weight of the UV-curable compositions.

Table 4

All UV curable compositions had a viscosity of less than 30 mPa.s at 45°C, making them suitable as UV curable inkjet inks.

Evaluation and results

A PET175 substrate was coated with Comparative Example COMP-1 and Inventive Examples INV-1 through INV-7 using a bar applicator and a 10 pm spiral bar. All coated samples were cured using a Fusion DRSE-120 carrier equipped with a Fusion VPS/1600 lamp (D bulb). The samples were cured three times at a belt speed of 20 m/min. and at the maximum power of the lamp. All samples fully cured.

Five people evaluated the odor of the samples, scoring each of them from 0, in case of a total absence of odour, to 5, in case of a very persistent odour. The mean of the five scores was obtained. The mean odor score is shown in Table 5.

Table 5

It is evident from Table 5 that the photoinitiators according to the present invention clearly improve the background odor of the cured samples. It was also observed that the addition of 20% by weight ethanol to the UV-curable compositions INV-5 and INV-7 did not affect the cure.

Claims (15)

1. Acylphosphine oxide initiator in which the acyl group is selected from the group consisting of a benzoyl group substituted by a urea group or an oxalylamide group, a 2,6-dimethylbenzoyl group substituted at the 3-position by a urea group, or a oxalylamide group, a 2,6-dimethoxybenzoyl group substituted in the 3-position by a urea group or an oxalylamide group, a 2,4,6-trimethylbenzoyl group substituted in the 3-position by a urea group or an oxalylamide group, and a 2,4-group 3-substituted, 6-trimethoxybenzoyl with a urea group or an oxalylamide group, with the proviso that the acylphosphine oxide initiator does not contain any thiol group if the acyl group includes a urea group. 2. The acylphosphine oxide initiator according to claim 1, wherein the acylphosphine oxide initiator is represented by Formula (I):

Formula (I), in which R1 represents a group according to Formula (II):

Formula (II), in which * represents the point of attachment to the phosphine oxide group in Formula I), R2 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or OR8, R3 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or a group represented by Formula (II), R4, R5 and R6 independently represent a hydrogen, methyl or methoxy atom, R7 and R8 independently represent a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted aralkyl group , a substituted or unsubstituted alkaryl group, a substituted or unsubstituted heteroaryl group, a group comprising (meth)acrylate or a group comprising (meth)acrylamide, and n represents the integer 0 or 1. 3. The acylphosphine oxide initiator according to claim 1, wherein the acylphosphine oxide initiator is represented by Formula (III):

Formula (III), in which R2 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or OR8, R3 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group or a group represented by Formula (II),

Formula (II), * represents the point of attachment to the phosphine oxide group in Formula (I), R4, R5 and R6 independently represent a hydrogen, methyl or methoxy atom, R7 and R8 independently represent a hydrogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, a substituted or unsubstituted C2-C10 alkynyl group, a substituted or unsubstituted aralkyl group , a substituted or unsubstituted alkaryl group, a substituted or unsubstituted heteroaryl group, a group comprising (meth)acrylate or a group comprising (meth)acrylamide, L represents a divalent linking group containing from 2 to 60 carbon atoms. carbon, and n represents the integer 0 or 1. 4. Acylphosphine oxide initiator according to claim 2 or 3, wherein R4, R5 and R6 represent methyl. 5. The acylphosphine oxide initiator according to any one of claims 3 to 4, wherein the linking group L is an alkylene group or an alkoxylated group. 6. The acylphosphine oxide initiator of claim 5, wherein the linking group L is further substituted by a group selected from the group consisting of:

7. The acylphosphine oxide initiator according to any one of claims 1 to 6, wherein the acylphosphine oxide initiator is a polymerizable photoinitiator, a polymeric photoinitiator or a multifunctional photoinitiator. The acylphosphine oxide initiator of claim 7, wherein the acylphosphine oxide initiator includes an acrylate-containing group. 9. Acylphosphine oxide initiator according to claim 1 selected from the group consisting of:

where n = 1 to 20,

10. UV radiation curable composition including a polymerizable compound and an acylphosphine oxide initiator according to any one of claims 1 to 9. The UV-curable composition of claim 10, wherein the UV-curable composition is a UV-curable inkjet ink. 12. Inkjet printing process including the steps of: a) applying a UV-curable composition according to claim 10 or 11 on a substrate, and b) UV-curing the UV-curable composition on the substrate. The inkjet printing method of claim 12, wherein the UV curable composition is applied by ejecting a UV curable inkjet ink onto the substrate. The inkjet printing method of claim 12, wherein the UV curable composition is applied as a primer or varnish. 15. Use of a composition curable by UV radiation according to claims 10 or 11 to obtain a printed article for interior decoration.